<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
    <p class="one two" id="test">hello</p>
    <script>
    /* classlist
      length-->获取长度
     */
     var classList=document.getElementById("test").classList;
     console.log(classList.item(1))
    </script>
</body>
</html>